The lamp should be small, so what is best than a LED!?
We used http://www.ikea.com/it/it/catalog/products/10237257/
and a very cheap microphone.
The result was much more nice than we expected!
Step 1: Empty the Microphone
We advise you to use a very cheap dynamic microphone.
We used a used AKG one, bought for about 15 euros.
Usually the cap can be screw off.
Step 2: Disassemble the JANSJÖ
You have to keep the led holder intact, it will be useful.
Step 3: Join Mic and Lamp
We used some strong glue to fix the lamp holder to the mic.
Step 4: Soldering, Sweet Soldering
I suggest you to try out the lamp ;) during this step.
Step 5: Make the Wire Black
We put some black sheath on it and changed the switch with a black one.
The last step was to place mic on the stand.